There are a variety of endoscopic procedures in which it may be desirable to irrigate a body cavity into which the endoscope has been placed. For example, among the more common endoscopic procedures requiring irrigation is in the surgical treatment of the joints (knees, shoulders, elbows, wrists and ankles) by arthroscopic surgery. Arthroscopic surgery is far less invasive than open surgical procedures and has become widely accepted. A typical arthroscopic procedure lasts about 45 minutes to one hour as compared to three hours for an open surgical procedure. Arthroscopic surgery enables the surgeon to directly visualize the anatomy of the joint in a less invasive and reduced trauma procedure. Significantly less anesthesia is required in an arthroscopic procedure as compared to open surgery. The recovery from an arthroscopic procedure typically is much quicker than from open surgery.
Arthroscopy provides for the direct visualization of the interior of a joint through a fiber optic endoscope referred to as an arthroscope. The procedure enables the surgeon to diagnose and treat damage to the joint. For example, torn cartilage and debris can be located and removed using instruments specifically designed for arthroscopic surgery. The procedure involves the insertion of instruments into the joint through small incisions made in the region of the joint. When the arthroscopic procedure is diagnostic, typically two instruments are inserted into the joint. When the arthroscopic procedure is therapeutic, typically three or more instruments are inserted into the joint.
One instrument common to all arthroscopic procedures is an arthroscope which has light transmitting optical fibers by which the interior of the joint may be illuminated and observed through an eyepiece or by coupling the output optical fibers to a video camera and displaying the image on a video monitor. The endoscope typically has one or more conduits through which irrigation liquid may flow into or out of the joint. In a diagnostic procedure, the second instrument typically will be a probe with which the surgeon may probe the interior of the joint while observing the interior of the joint through the endoscope.
In either a diagnostic or a therapeutic arthroscopic procedure, it is necessary to cause irrigation liquid to enter the joint under pressure. The irrigation liquid, usually saline solution, serves a number of purposes. The joint compartment normally is compressed and provides little room for the endoscope or the arthroscopic instruments. In order to provide room for the endoscope and the instruments and to enable the surgeon better to see all regions of the joint, the irrigation fluid is admitted to the interior of the joint under pressure to cause the joint to become distended. Once the irrigation solution has distended the joint, the surgeon has more room to manipulate the endoscope and the instruments as is necessary to perform the procedure. A further important effect of pressurizing the joint is to provide a tamponading effect, such as to minimize bleeding within the joint. The pressure, which is above the patient's blood pressure, tends to close off bleeding capillaries in tissue that may have been cut during the procedure. This is particularly important in situations where tourniquets are neither convenient nor effective, such as in the shoulders.
Distension of the joint is controlled by maintaining a desired level of pressure in the joint and by balancing the inflow and the outflow of irrigation solution. If the outflow exceeds the inflow, the joint will collapse and the surgeon must delay the procedure until distension is achieved. Distension may be maintained either by maintaining a continuous inflow and outflow at the joint or by intermittently closing both the inflow and the outflow while the surgeon works within the joint space and then, after the solution becomes murky, reestablishing inflow and outflow to flush the area with fresh solution. In either instance, controlling the flow rate is necessary to achieve sufficient distension without creating excessive intra-articular pressure. It is important to monitor the intra-articular pressure throughout the arthroscopic procedure and, to do so, surgeons frequently feel the outside of the joint to evaluate the bulges caused by the distension.
In a therapeutic arthroscopy, the amount of irrigation fluid flowing through the joint typically is greater than that when the procedure is merely diagnostic. The additional flow requirements result from the fact that the procedure will generate a considerable amount of debris which must be flushed from the joint not only to avoid post-operative complications from the procedure but also to facilitate the surgeons continued visualization of the interior of the joint.
A commonly used technique for irrigating the joint is by gravity flow of irrigation solution from an overhead supply. To that end, irrigation bags containing irrigation liquid are hung at a height of about 6 to 8 feet above the patient. A tube leading from the bags is connected to one of the ports of the arthroscope or to a separate irrigation cannula which will have been inserted previously into the joint. The tube typically is provided with a clamp which, when opened, enables the irrigation liquid to flow by gravity into the joint. A pulley system often is utilized so that the attending nurse can lower the bags and change them as they empty. By way of example, between about 3 to 15 liters of irrigation liquid typically are used on a knee arthroscopy although in some cases as many as 30 liters might be used. With the gravity system, the pressure of the irrigation liquid applied to the joint is dependent on the height of the bag containing the irrigation liquid.
The gravity system is awkward and presents a number of difficulties. For example, with some patients, particularly muscular patients, the gravity flow system does not distend the joint very effectively. Additional pressure is required. Many surgical facilities do not have sufficient height to raise the bag distend the joint under such circumstances. Typically, this results in the necessity for an attending nurse to squeeze the irrigation bag continuously throughout the entire arthroscopy procedure. Also among the difficulties with the gravity system is that when a bag approaches being empty and must be changed, it must be pulled down from its elevated position. That reduces the fluid pressure in the joint and risks loss of distension.
As an alternate to the gravity system, a number of pumping systems have come to be used for irrigation. Many of such pumping systems have been cumbersome, complex and expensive. Among the types of pumps that have been used are a roller pump or a piston pump. Neither type of pump is adapted to convert from pumped flow to gravity flow. Thus, should such a pump fail during a procedure, it would be necessary to terminate the procedure and reconfigure the irrigation system to permit continued flow. Additionally, such devices typically are electrically powered which adds some measure of risk in view of the wet, conductive environment in which the device is used. Moreover, such pumps do not allow for continuous low pressure (gravity) flow. Continuous gravity flow often is considered important when it is desired to infuse cold irrigation solution without application of additional pressure such as to provide a tamponade effect by the cold temperature alone. Typically, such a procedure may be performed after the completion of the surgery.
An improved arthroscopic irrigation pumping system that avoids the foregoing difficulties is disclosed in U.S. application Ser. No. 387,712 filed Jul. 31, 1989. That system incorporates a pneumatically driven pulsatile pump in the flow conduit from the irrigation liquid reservoir to the inlet cannula inserted in the joint. As described in that application, the pump is effective to develop and maintain effective distension in the joint while also permitting continuous gravity flow when desired.
Recent improvements in arthroscopic surgical instruments have resulted in devices, such as shavers, cutters and the like that are intended to operate at high speeds. These devices tend to generate debris at a relatively high rate and, therefore, require relatively high flow rates of irrigation liquid through the joint to flush debris as well as to maintain an ability to observe the interior of the joint. Many of such devices incorporate an aspiration channel through which debris and liquid may be suctioned out of the joint. When such devices are operated, it is necessary to increase the flow of irrigation liquid into the joint in order to compensate for the lost liquid so as to maintain the distension of the joint. With irrigation systems that use motor driven piston or roller pumps, the increased flow into the joint is developed by increasing the speed and output of the pump. Typical of such devices are those described in U.S. Pat. Nos. 4,820,265; 4,902,277 and 4,940,457. Such systems usually require sensors for sensing the pressure within the joint and a feedback and control system for controlling operation of the pumps in response to that feedback. Such systems are cumbersome and expensive.
The type of system described in U.S. application Ser. No. 387,712 filed Jul. 31, 1989, although arranged to permit gravity flow, may not permit fluid flow at a sufficiently high rate to maintain joint distension when used in conjunction with some high speed, high flow rate shavers and similar instruments. It would be desirable, therefore, to provide an improved arthroscopic irrigation system that is inexpensive and easy to use yet which enables high flow rates in order to meet the demands of high suction arthroscopic instruments. Additionally, it would be desirable further to improve the device described in U.S. application Serial No. 387,712 filed Jul. 31, 1989 to include such an arrangement. It is among the general objects of the invention to do so.